Saving wildlife might be good for your health

Preserving nature increases biodiversity — and that leads to lower rates of disease.

In areas with high biodiversity, there's a lower chance ticks will feed on one of its primary hosts, the white-footed mouse, so the risk of Lyme disease for humans drops.
(Photo: Charles Homler/Wikimedia Commons)

Preserving habitats and encouraging biodiversity does
wonders for plant and animal life, giving them room to thrive without human
interference. In recent years some scientists have wondered if
biodiversity might also help humans, protecting us from infectious diseases
that spread from nonhuman animals to people.

The idea first started with ecologists Richard Ostfeld and Felicia
Keesing. They called it the “dilution
effect,” a theory based on an in-depth look at Lyme disease and one of its
primary hosts, the white-footed mouse. They found that in areas with greater
biodiversity, specifically, more host species, the risk of Lyme disease to
humans was actually reduced.

The Cary Institute describes the phenomenon this way:

“When host diversity is high, there is a lower probability that
ticks will feed on a white-footed mouse host. Larval ticks are less likely to
become infected with B. burgdorferi when they feed on other vertebrate animals,
such as chipmunks, lizards, or ground-dwelling birds. When ticks obtain their
larval blood meal without becoming infected, they are not dangerous to humans
when they feed as nymphs the following year.”

Now, that theory is getting some extra padding, with two more
recent studies backing up its claims. And not just with Lyme disease. In 2014
researchers studied
data
on diseases, public health services, climatic factors and
conservation policies in the Brazilian Amazon and found that incidences of
malaria, acute respiratory infection (ARI) and diarrhea were reduced in protected
areas.

The authors concluded that incidence rates of those illnesses would be reduced by increasing protected areas and malaria rates could be lessened even more by restricting roads and mining. The authors said, "Although these relationships are complex, we
conclude that interventions to preserve natural capital can deliver cobenefits
by also increasing human (health) capital.”

A 2015 study found
similar results, investigating the claim that the rise in disease and the fall of
biodiversity were directly related. They too, based on the data, believe that
the two are linked, noting that “declines in biodiversity could increase human
and wildlife diseases and decrease crop and forest production.”

That’s not to say that these studies prove the dilution effect
without a doubt. As the authors of the Brazilian Amazon research wrote, the
evidence is “thin” or, perhaps more accurately, in need of further research.

Not everyone is convinced, some
believing
that other factors could be to blame for the link between a lack
of biodiversity and an increase in disease. Or it might be true in some cases,
such as Lyme, and not true in others. The correlation would need to be
investigated on a case by case basis.

It's safe to say that biodiversity is important, whether for
human health or the health of the planet. However, due to invasive species, the
impact of climate change and humanity’s consumption of Earth’s resources,
biodiversity
has long been on the decline.